Utilizing Colloidal Liquid Activated Carbon to Control Back-Diffusive Mass Loading at Three Midwest Sites with Glaciogenic Interbedded Geology
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The document presents three case studies utilizing colloidal liquid activated carbon for remediation of chlorinated solvent groundwater plumes in Midwest sites with interbedded glacial geology. The method effectively mitigated back-diffusive mass loading from clay formations, achieving over 95% reduction in target contaminants within two quarters. Continuous design verification ensured proper injection and distribution of the activated carbon across the treatment zones, demonstrating the technique's effectiveness and potential long-term benefits.
Utilizing Colloidal Liquid Activated Carbon to Control Back-Diffusive Mass Loading at Three Midwest Sites with Glaciogenic Interbedded Geology
- 1. RESEARCH POSTER PRESENTATION DESIGN © 2015 www.PosterPresentations.com SITE 1 COLLOIDAL LIQUID ACTIVATED CARBON ONLY SITE 3 COLLOIDAL LIQUID ACTIVATED CARBON ELECTRON DONOR BIOAUGMENTATION Keith M. Gaskill, LPG; Douglas A. Davis; Steve Barnes EnviroForensics, LLC (EnviroForensics) and Regenesis, Inc. MATERIALS AND METHODS ABSTRACT Utilizing Colloidal Liquid Activated Carbon to Control Back-Diffusive Mass Loading at Three Midwest Sites with Glaciogenic Interbedded Geology SITE 2 COLLOIDAL LIQUID ACTIVATED CARBON ELECTRON DONOR BIOAUGMENTATION Three individual case studies have been compiled to demonstrate a remediation technique intended to achieve similar results at each individual site. All of these sites are impacted with chlorinated solvents with groundwater plumes that are considered to be mature stage. Which means that mass loading is occurring from clay formations above, below, or within the sand unit transporting the dissolved phase plume. In these cases, most of the chlorinated solvent mass that would result in loading into the transport zone has been remediated or attenuated. Back diffusion is a common and well understood late plume phenomenon that slowly continues to load the plume for many years into the future if not treated. Colloidal Liquid Activated Carbon (PlumeStop) from REGENESIS was applied to sandy transport zones surrounded by clay storage zones to sequester chlorinated solvent mass diffusing from the clay units. The approach included initial and continual design verification over the aerial extent of the injection area. The initial verification at two of the sites established the radius of influence that the transport zone would allow. The continual design verification was needed to confirm the injection interval and potential dosing alterations within each injection zone. The distribution analysis, where conducted, demonstrated a complete coverage of the sediments within the transport zone and along the clay units in contact with the sand. This indicates that the liquid activated carbon is properly distributed and should be effective in removal of back diffused contaminants and will theoretically be effective for a significant time period unmatched by other technologies based on manufacturer’s estimates. SITE 3 RESULTS AUTHORS 0 1,000 2,000 3,000 4,000 1/31/2016 5/10/2016 8/18/2016 11/26/2016 3/6/2017 6/14/2017 9/22/2017 12/31/2017 4/10/2018 PPB DATE MW-7 PCE and TCE PCE TCE Remediation 0.0 50.0 100.0 150.0 200.0 5/10/2016 8/18/2016 11/26/2016 3/6/2017 6/14/2017 9/22/2017 12/31/2017 4/10/2018 PPB DATE MW-10 PCE and TCE PCE TCE Remediation 0 200 400 600 800 1000 1200 4/1/2012 8/14/2013 12/27/2014 5/10/2016 9/22/2017 2/4/2019 PPB DATE PCE at MW-1 and MW-6 MW-1 MW-6 Remediation 0.0 20.0 40.0 60.0 80.0 100.0 4/1/2012 8/14/2013 12/27/2014 5/10/2016 9/22/2017 2/4/2019 PPB DATE PCE at MW-2, MW-4 and MW-5 MW-2 MW-4 MW-5 Remediation Remediation Objective: Obtain closure by eliminating back diffusion flux from PCE and daughter products into the sand transport zone. Minimize daughter product formation and minimize rebound. Main soil source removed through excavation. Design Verification: Prior to injection activities, EnviroForensics and REGENESIS Remediation Services (RRS) advanced 8 soil cores in the injection area to verify the desired injection zone thickness and depth to ensure an effective application. The target injection zone varied by as much as five feet in depth and three feet in thickness. The design verification proved to be very valuable in this type of injection to assure prevention of back diffusive mass loading. Cores were collected before and after the injection event. Remediation Design: • 6,393 gallons of reagent solution was pumped into 24 direct push injection points in a grid pattern at a concentration of 6,000 mg/L. Remediation Objective: Obtain closure by eliminating back diffusion flux into the sand transport zone in two distinct areas. The source area required increased dosage and volume per point. The dilute plume mass area was treated by a barrier wall to prevent downgradient migration. An electron donor to aid in enhanced biological reduction was injected for utilization by naturally occurring microbes. The microbe population was also augmented. Remediation Objective: This project was completed as an interim measure to remediate onsite TCE impact for a financial transaction as well as to provide a line of evidence in identifying multiple offsite/downgradient sources to the overall plume. The chlorinated solvent plume is shown on the above-left figure. Remediation Design: • In the source area; 3,836 gallons of reagent solution was injected into 6 semi-permanent 1” PVC injection points in a semi-grid pattern. • A barrier wall consisting of 4,795 gallons of reagent solution injected into 12 points was completed • Dosing consisted of a concentration of 6,000 mg/L. • A total of 660 pounds of electron donor and 17 liters of bioaugmentation substrate was injected in total. Design Verification: Prior to injection activities, EnviroForensics and RRS advanced 3 soil cores in the injection area to verify the desired injection zone thickness and depth. Two cores were collected along the barrier wall, while one was collected near the location of the interior borings. The verification allowed for changes to be made to the initial design. Due to experiencing tighter soils than expected, the barrier was extended from 10 points to 12 to account for the smaller expected ROI. Indoor drilling constraints and space issues limited the interior borings from 10 to 6. Thus, the volume and dosage of the injectate was similarly adjusted as the project progressed. Representative section of sandy zone of profile before injection event Representative section of sandy zone of profile after injection event. Note coloration change due to activated carbon addition Remediation Design: • The above-right figure shows the injection grid and barrier sectioned out to account for the size of the site and variability in geology and plume concentration. • The west grid (sections 1-4) represents the most impacted area and had 11,504 gallons of reagent (20,000 mg/L) injected along with 3,600 pounds of electron donor with 35 liters of bioaugmentation substrate. • The east grid (sections 1-7) had 24,766 gallons of reagent (15,000 mg/L) injected along with 5,400 pounds of electron donor and 64 liters of bioaugmentation substrate. • The barrier wall had 22,000 gallons of reagent (5,000 mg/L) injected along with 1,530 pounds of electron donor and 16 liters of bioaugmentation substrate. Design Verification: Prior to injection activities, EnviroForensics, REGENESIS technical staff, and RRS first conducted a Radius of Influence (ROI) test to determine if the planned ROI was adequate to accomplish remediation plans. A point of initial injection was selected, and observation points were installed at distances of 5 ft, 7.5 ft, 12.5 ft., and 15 ft. During the test, the reagent was injected and bailers in each of the observation locations were utilized for visual evidence of the reagent. The fluid was observed in the 12.5 ft. distance, but not the 15 ft. distance verifying the conservatively designed spacing of 20 ft. between points in the interior grid areas would be sufficient to ensure lateral coverage The second phase of verification testing to was establish distribution within the transport zone of the soil. After the ROI testing was completed, a soil core was collected 5 feet from the injection point examine and confirm distribution of the liquid activated carbon substrate through the transport zones. Shown on the right is the core collected nearby the ROI injection location for a distribution analysis. Ongoing Design Verification: As the remediation project advanced, a test soil boring was advanced at each treatment zone section to establish the depth and thickness of the sand unit. Many times over the course of this remediation project; the number of points, dosing within points, order of points (to keep the warehouse operation active), and site logistics such as deliveries of product and water, had to be continually updated by the REGENESIS, RRS, and EnviroForensics project team. A QuantArray-Chlor (Microbial Insights) biological assessment of dechlorinating microbes was completed both before and shortly after the injection event. The results showed a distinct bloom in microbial populations in groundwater indicating that the carbon sites were bioavailable and the remedial action was proceeding as planned. Above: The ROI testing location. Pumping was started at the location to the left and observed at the three points to the right. Above: Core completed after injection event. Note colloidal liquid activated carbon in the fourth core section and part of the fifth (left to right). This 16-22 foot depth represents the targeted transport zone sand lens. Above: After the injection event, the water in most monitoring wells in the injection area were found to have liquid activated carbon in groundwater collected from them demonstrating proof of concept. Above: A core completed following the ROI testing revealed the activated carbon present in the sand seam. Above: Colloidal Activated Carbon observed in groundwater at a point 5 feet from the pumping location. Figure demonstrates the design principle for back diffusion control. Target the sand transport zone that is experiencing matrix diffusion from the clay storage zones thereby sequestering the contaminants for subsequent bioremediation. Baseline Concentration Contour Map • TCE impact present on the target property and extends offsite to the southwest. 192 Day Post-Remediation Concentration Contour Map • TCE impact removed from the target property • Potential offsite source(s) to the south and southwest appears likely. 101 Day Post-Remediation Concentration Contour Map • TCE impact almost removed from the target property yet extends offsite to the southwest. • Potential offsite source(s) to the south and southwest potentially identified. 31 Day Post-Remediation Concentration Contour Map • TCE impact greatly reduced on the target property yet extends offsite to the southwest. CONCLUSIONS • Colloidal Liquid Activated Carbon was applied to three sites in Midwestern glacial terrain where a transport sand unit was underlain and overlain by storage clay units. Back diffusive loading to the sand unit was occurring in each case. • The objective at each site was to control back diffusion mass loading to a transport sand unit. • In each case, greater than 95% reduction has occurred in target compounds in two quarters or less. Keith M. Gaskill. LPG, Chief Geologist, EnviroForensics, Indianapolis, IN kgaskill@enviroforensics.com Douglas A Davis, Senior Design Specialist, Columbus, OH ddavis@regenesis.com Steve Barnes, Remediation Services Director of Operations, Mishawaka, IN sbarnes@regenesis.com